By HENRY FOUNTAIN

In a finding that is sure to add to one of the longest-running debates in music, a detailed analysis of the varnish on five instruments made by Antonio Stradivari reveals that he coated the wood with a rather ordinary mix of oil and resin. Those looking to the varnish as the secret to the master Italian violin maker’s renown, the study suggests, had best look elsewhere.

“It’s a very basic recipe,” said Jean- Philippe Echard, a chemist at the Musee de la Musique in Paris, who, with other researchers in France and Germany, analyzed tiny samples of wood and varnish from the museum’s Stradivarius collection, four violins and a viola d’amore dating from 1692 to 1724.

Their study, published online by a German chemistry journal, Angewandte Chemie International Edition, found that a drying oil, linseed or walnut, was used as a first coat to seal the wood. That was followed by a coat of oil and pine, fir or larch resin, with red pigments added in all but the earliest instrument. The recipe was probably little different from that used in the town of Cremona. “The ingredients were simple, so probably the skill was in his hand and eye,” Mr. Echard said.

In the centuries since Stradivari’s death, musicians, critics and luthiers - makers of stringed instruments - have debated what gives many of his 600 known instruments their brilliant tone. Perhaps it was the wood he used or the patterns he developed . Or perhaps, some suggested, there was a secret ingredient in his varnish - egg or animal-hide proteins in the base coat, and amber, myrrh or some other more exotic substance in the top coat - that stiffened the wood just so.

Earlier studies had found traces of minerals and proteins in the wood . One group found evidence of volcanic ash; another suggested that bacteria or fungi played a role.

In a study published in The Strad magazine, Stewart Pollens, a former conservator of musical instruments at the Metropolitan Museum of Art in New York, found evidence of proteins and gums, although, like the European group, he suggested the varnish was largely oil and resin.

But studies of Stradivari’s varnish have been hampered by the lack of samples, which is understandable given the rarity, and value, of the instruments.

Douglas Cox, a violin maker in West Brattleboro, Vermont, said he was not surprised . “The simplest explanation is most likely to be true,” he said. The recipe “is not all that different from varnishes found on fine furniture from the same area.”

Mr. Echard said Stradivari took a painterly approach to finishing his instruments. The pigmented top coat, he said, may have been applied the way Rembrandt or Titian applied glazes to soften flesh tones. Perhaps that, Mr. Echard suggested half-jokingly, is what makes some of Stradivari’s violins special.

“Maybe a player, when seeing a beautiful instrument, he plays better,” he said. “Maybe this is the secret.”

Research revealed that Stradivari used a mix of oil and resin. / PHILIPPE WOJAZER/REUTERS